#include <bits/stdc++.h>

using namespace std;

int minimumNumber(int n, string password) {
    // Return the minimum number of characters to make the password strong
    
    int fA = 0;
    int fa = 0;
    int f1 = 0;
    int fc = 0;
    
    for(int i=0;i<n;i++){
        if(password[i]-'A' >= 0 && password[i]-'A' < 26){
            fA = 1;
        }
        else if(password[i]-'a' >= 0 && password[i]-'a' < 26){
            fa = 1;
        }
        else if(password[i]-'0' >= 0 && password[i]-'0' < 10){
            f1 = 1;
        }
        else{
            fc = 1;
        }
    }
    
    int k = f1 + fa + fA + fc;
    
    if(n >= 6 && k == 4){
        return 0;    
    }
    else if(n >= 6){
        return (4-k);
    }
    else{
        return max(6-n,4-k);
    }
    
}

int main() {
    int n;
    cin >> n;
    string password;
    cin >> password;
    int answer = minimumNumber(n, password);
    cout << answer << endl;
    return 0;
}